Thank you for the response. Practicality dictates going this route. I'm concerned with damaging my relationship with one of the instructors no matter which way I decide.
I can see that being a concern, but why don't you go to the one you won't be ranking with and simply say, "Since I am going to two organizations at this point, I was wondering what your feelings are on my choosing to rank with Sensei B. Since I need to make a decision, and they are much closer to me, it seems more practical to rank with them. Are you ok with that?"
I find most of these guys are pretty understanding, and if you lay out your reasoning for what you are doing, they will be ok with it. The key to avoiding hurt feelings is explaining what you are doing clearly, and your logic behind your decision, and finally asking them what they think.